This application is submitted in response to an invitation to apply for funds under the Small Grant Program for NIDDK K08/K23 Recipients (PAR-01-066). If awarded, this RO3 grant would provide supplemental funding during the final two years of the applicant's K08 award (DK02944). The additional funding would provide crucial resources, such as technical assistance, that would enhance the applicant's ability to compete for further grant support and would facilitate the transition to full independence. This application proposes two lines of investigation which will build upon and extend ongoing studies of the cell biology of glutamic acid decarboxylase (GAD) in the pancreatic islets. I have found that, surprisingly, the vesicular GABA transporter VIAAT is absent from rat beta cells and human islets. This suggests that there is an as yet unidentified GABA transporter which, I hypothesize, interacts specifically with GAD65. With assistance from the laboratories of Drs. Jay Heinecke and Stanley Fields, I will seek to identify beta-cell proteins that interact with GAD65 and that may therefore influence its trafficking and perhaps its discharge from injured islets. The impetus for the second line of investigation is the importance of detecting GAD65 release in vivo together with my success in developing a sensitive, prototype, blood GAD65 assay. Damage to tissues such as myocardium and liver can be detected and monitored by serum assays for discharged proteins. In contrast, metabolic tests reveal only extensive islet damage after the fact. I hypothesize that a plasma assay for GAD65 will provide a means to detect and monitor ongoing beta-cell damage in individuals with diabetes and asymptomatic insulitis and in animal models of autoimmune diabetes. Such a test would be invaluable for a variety of applications, including investigating the pathogenesis of islet injury and autoimmunity, helping identify candidates for preventative therapies and monitoring transplanted islets for rejection. My goal is to complete the development and validation of a highly sensitive, plasma assay for GAD65 and to conduct a preliminary analysis of plasma GAD65 levels in control and diabetic subjects and in BB rats prior to and after the onset of diabetes. Data generated by these studies will form the basis of further investigations of the intracellular trafficking of GAD65 as well as of in vivo studies of the time-course, triggers and clinical utility of monitoring GAD65 discharge.